1. Field of the Invention
The present invention relates to devices for holding objects or workpiece and, more particularly, to a holddown device having 360.degree. swivable maneuverability for moveable attachment to various tools and tables
2. Description of the Prior Art
During cutting, drilling, and performing other machine tool operations upon a workpiece, it is vital that the workpiece being acted upon is securely held in place, whether the workpiece is on a drill press, a mill table, a welding table, a workbench, or otherwise. Should the workpiece move or slip while the operator is performing an operation on the workpiece, the unsteady workpiece can spin, break, splinter, or be propelled away from the work table
Various devices have heretofore been devised for retaining variously-shaped workpieces on work surfaces during machining operations, including parallel clamps, C-clamps, angle plates, jackscrews, step blocks, V-blocks, flat straps, U-straps, gooseneck straps, and specialty clamps designed to work with particular tools. These devices, however, are tolerably effective in holding the workpiece since in most instances two or more of them must be cooperatively utilized in order to securely retain the workpiece. It is cumbersome and timeconsuming to set up the workpiece holding apparatus for possibly only one operation thereby adding to the labor cost and the possibility of problems due to the interaction of the various pieces.
One prior art clamping device is shown in a tool catalogue from Woodcraft of P.0. Box 1686, Parkersburg, W. Va., and consists of a notched shank or post that rests in a table-mounted collar having matched ridges within the collar to prevent slipping of the post. A non-moveable transversely-extending arm is formed at the top of the post distal the table surface, the arm having on its extended end, a pivoting second arm. The second arm has a pivoting foot portion for holding against the workpiece and an internally threaded bushing on the other end accommodating a threaded screw that angles against and tightens on the distal end of the post throwing the post off the perpendicular so it binds to the collar
Several problems associated with this type of prior art clamping device are its manner of adjustability, its ease of adjustability, and its adjustability with respect to the workpiece. First, the height of the post is adjustable only in discrete steps defined by the notches in the post and the associated rings in the collar. Second, if the height of the post is adjusted, the second arm must pivot about its axis either upwards or downwards changing the location on the workpiece that the foot contacts. In order to remedy this, the location or orientation of the workpiece must be changed in order for the foot to contact the same location Third, the second arm has only a limited range of motion defined by the pivot and the practical length of the threaded screw in being able to contact the post.
Another prior art clamping device is shown in U.S. Pat. No. 3,575,373--Reinhardt et al. entitled "Holddown Device." There, a flat arm extends essentially perpendicular to and is movable on a central post. Extending from the distal end of the arm, relative to the post, is a spring-biased holding pad for contacting the surface of the piece to be held down The arm is canted on the post by the pressure of the biasing spring
This prior art clamping device is disadvantageous in that it cannot clamp down on a workpiece with enough force to prevent the workpiece from moving, especially when the workpiece needs to be drilled, milled, or otherwise, and is particularly designed to be used in conjunction with a plurality of the same devices for holding gas meters, or the like, during transportation.
In addition, holddown devices of the prior art are limited in their range of movement due to their mounting location or physical constraints such that orientation of the workpiece is confined to the range of movement of the holddown device. Further, most devices of the prior art cannot accommodate workpieces having vastly different thicknesses. Also, with prior art devices that purportedly allow vertical and/or horizontal clamping, either the devices cannot accommodate both or they are not reliable enough to securely hold the workpiece Further, transportability and adaptability of the prior art holddown devices to various machines and tables is extremely limited and in most instances the prior art devices are confined to the location in which they are originally installed.
It is thus an object of the present invention to overcome the shortcomings of the prior art and provide a simple, yet effective workpiece holddown that is also extremely versatile and readily transplantable.